There are a vast variety of conventional fabrication methods and devices used from a variety of operational systems. As examples, industrial arts have been used for making glass and ceramic components. The tool and die arts have been used for making molded glass and ceramic components. Molded components include poured, injected and stamped glass ceramic components. The semiconductor arts have been used for fabricating semiconductors, chips, and hybrids. During fabrication, depositing conductor traces and with feedthroughs are used to form an electrical communications grid about the semiconductor components. The microelectromechanical systems (MEMS) arts have been used for making active and passive MEMS sensors and actuators, among others devices. The wafer flip and bond arts have been used for electrically connecting and encapsulating electrical devices, MEMS devices, and optical devices within flip-bonded semiconductor and ceramic substrates. The electrical arts have been used for making batteries, power converters, communications processors, and RF antennae, among others. The electronic arts have been used for making power supplies, electronic devices, optoelectronic devices, RF transmitters, RF receivers, and despreading correlators, among others. The electromechanical arts have been used for making active gyros, and accelerometers, among others. The photonic arts for have been used for making optical transceivers, optical detectors, mirrors, splitters, reflectors, polarizers, lens, and optical fibers, among others, for communicating and processing optical signals for use in an optical communications grid. While there is a vast array of technologies available, system integration of various technology is limited due to operational compatibility and fabrication feasibility.
One example of an intertechnology integrated system is a conventional satellite. A satellite can be made of silicon for exploiting strength, high thermal conductivity, infrared transparency, and radiation-shielding properties of silicon along with established silicon microelectronics and microelectromechanical systems fabrication techniques to create satellites composed of silicon components. Silicon is an excellent choice as the main material for a spacecraft, but bulk mechanical, thermal, and optical properties cannot be significantly modified.
Glass materials have an amorphous state that is a noncrystalline state. Ceramic materials have a crystalline state. Ceramic materials are tougher than glass but also tend to be more brittle than the glass, and hence not generally suitable as a support structure in high tensile stress application. Glass is weaker than ceramic, and susceptible to breakage during wide temperature operating range variations, but glass has superior optical transmission characteristics and can be brittle. Ceramics can withstand higher temperatures than the glass, but have poor optical transmission characteristics. Glass and ceramic materials differ in material properties, such optical transmission, electrical conductivity, thermal conductivity, and chemical resistance, offering operational incompatibility, and unsuitability for common use in a given application. Glass materials have been annealed to reduce internal stresses and prevent cracking and breakage during cooling, especially for thick components. This is typically accomplished by heating glass to its softening temperature, followed by a slow cool-down process. Annealing decreases the overall strength of glass, but also makes the glass less brittle. Ceramic materials can also be annealed, but it is usually used to improve strength. Ceramic annealing changes crystal grain size. Glass materials have been tempered to increase internal compressive stresses for increasing the strength of the glass to external tensile loads. This is typically accomplished by heating glass to its softening temperature, followed by a rapid cool-down process. Ceramic materials are not tempered.
Glass ceramic materials have portions in the amorphous state and portions in the crystalline state. Glass ceramic materials incorporate an in-situ nucleation process that results in the crystallization of the amorphous glass phase. This conversion process is nominally called devitrification. Typically, glass stock is produced with additional ingredients that upon heating above a specified temperature, induces ceramization of the material. The bake method provides a material that is controllably devitrified, that is, a controlled in situ precipitation of crystalline material within an amorphous glass body. Beyond the known advantages of glass and ceramics, glass ceramic materials offer cost-effective manufacturing of shaped ceramic parts. The initial material in the glass phase is melted and molded into the desired shape and then converted to the crystalline ceramic state. Because the resulting material is not 100% crystalline, but a composite of amorphous and crystalline phases, it is less brittle than true crystalline ceramics. Glass ceramic materials are used in a wide range of applications from specialized optics to consumer cookware. Some well-known trade names are Macor which is machinable ceramic Corning Corporation, Dicor which is a biomaterial from Corning Corporation, Zerodur which is an expansion material from Schott Corporation, ML-05 which is a magnetic material from Nippon Electric Glass Company, and Pyroceram which is a cookware material from Corning Ware.
A special category of sensitized glass ceramic material is the photostructruable glass ceramic materials, also called photositalls and photocerams. Photostructruable glass ceramic materials differ from most glass ceramic materials in that photosensitive agents are incorporated into the raw material. Upon photo excitation, these agents initiate a reaction that can lead to nucleation and crystallization, that is, ceramization, of the glass during a controlled bake process. One set of bake cycles leads to the formation of a metastable crystalline state which is soluble in hydrofluoric acid (HF). Another set of bake cycles leads to the formation of a stable crystalline state that is resistant to etching by both acids and bases. Photostructurable glass ceramic materials can be photolithographically patterned, and upon baking, only those patterned areas would be converted to one of the ceramic states. The exposure process is typically done using a flood-fill light source through an opaque mask resting directly on top of the photostructurable glass ceramic material. Patterning of the photostructurable glass ceramic material can be done by creating the metastable state and etching away this state in HF. An additional flood exposure and bake to the stable crystalline state will result in a patterned ceramic component. One example of a photostructurable glass ceramic material is Foturan of Schott Glass Works, Mainz, Germany that requires ultraviolet light for photoexposure and baking to temperatures above 500C.
Photostructurable glass ceramic materials can also be patterned using lasers that selectively expose parts of the material. Photostructurable glass ceramic materials can be micromachined with three-dimensional precision as an optically patterned component by direct-write laser milling, direct-write laser exposure followed by a chemical etching step to remove exposed volumes, or by photolithographic patterning followed by a chemical etching step to remove patterned areas.
The photostructurable glass ceramic material can be used to make components for various applications. For example, photostructurable glass ceramic materials have been used as a substrate and structure component in a multi-thruster propulsion system for a spacecraft also having metallic structural components with coupled semiconductor electronics on printed circuit boards. The propellant tank, propellant feed lines, and thrusters are all composed of micromachined photostructurable glass ceramic material, while the remaining components include batteries, electromagnetic solenoid valves, the pressure and temperature sensors, the fill and drain valves, and the electronics. The glass ceramic thruster substrate is supported in a metallic support structure providing structural support for the spacecraft. One problem associated with conventional metallic support structure is the mix of various supporting components and their various differences in thermal expansion coefficients, thermal conductivity, and optical properties that need to considered over the operational temperature ranges. In addition, silicon and metallic support structures require the use of harnesses and cables to route electrical lines about the spacecraft. In addition, silicon and metallic support structures block visible optical transmission, limiting optical communications paths about the silicon or metallic support structures. Further, silicon and metallic support structures have different material strengths rendering portions providing uneven structural strength about the support structure. Further still, silicon and metallic support structures have limited molding and precise patterning manufacturing methods. These and other disadvantages are solved or reduced using the invention.